What does a light 4-pin tell you? I have been getting those lately and trying to understand what it means when my balls are hitting light.

A light 4 pin can mean several things. You could be playing too far in the oil, not getting the ball out to the right board at the breakpoint, throwing it too fast, playing too deep to begin with, encountering carrydown, not using the correct ball for the condition or not getting enough lift on the ball.

I've left quite a few light 4s myself in the past four or five months. With me its usually I'm too much in the oil and the ball skids a little farther than usual. A few times its been throwing the ball too fast or lack of lift and on a couple of occasions a combination of several or all of the reasons.

a light 4 pin would occur if you came in light enough that the headpin just brushed the front of the 2 pin, sending the 2 pin back. The headpin would then bounce off of the sidewall back in front of the 4, or into the 7. It's like a "wall shot" or "bucket crumbler" or "rack shredder" where nothing manages to touch the 4. Adjustment would be about the same as if you had left a 2 pin.